The present invention relates to a magnetic tape loading method and apparatus for initially loading a magnetic tape of a predetermined length onto a tape winding body from a roll of "raw" magnetic tape of an article width, for rewinding a magnetic tape previously wound on a tape winding body to transfer the magnetic tape to another winding body, for loading a wide raw magnetic tape having a width larger than the article width, and for winding a plurality of raw article tapes cut from a wide raw tape having a width larger than the article width.
The known processes for manufacturing magnetic tapes, such as audio cassette tapes, video cassette tapes, memory tapes, broadcast-type video tapes, and the like include a process for winding a magnetic tape of a predetermined width onto a small-diameter tape winding body such as a reel, a hub or the like from a raw magnetic tape supply, a winding and rewinding process in which a magnetic tape which has been previously wound on a tape winding body is transferred from the tape winding body to another tape winding body, a process for winding a wide raw magnetic tape having a width larger than the article width, a process for winding a plurality of raw article tapes cut from a wide raw tape having a width larger than the article width, etc.
In the case where a magnetic tape is wound on a tape winding body using such winding or rewinding processes, various tape winding characteristics, such as vibration in the direction of tape thickness, vibration in the direction of tape width, and the like change according to the physical properties of the raw magnetic tape, the physical properties of the tape winding body, and the physical properties of the magnetic tape itself. As a result, a problem arises in regard to the winding appearance (winding condition) of the magnetic tape wound on the tape winding body. That is, winding difficulties arise so that the edges of the tape are uneven. Particularly, as the tape running speed during winding is increased, the tape edges become more uneven.
Of course, a magnetic tape in which the tape edges are uneven has a poor external appearance when the tape is placed in a magnetic tape cassette. Further, there arises a problem in that the tape edges can easily be damaged to thereby induce various problems, including deterioration of the electromagnetic conversion characteristics of the tape. Winding disorders become more serious as the density of recording is increased because, for example, a video magnetic tape must record both an audio signal and synchronizing signals in the vicinity of the tape edges.
Therefore, with the prior art magnetic tape manufacturing processes, all tapes had to be visually checked as to their winding appearance. This adds significantly to the total cost and time required in the manufacturing process.
To reduce the amount of manual inspection required, and for the purpose of improving the winding appearance, a method termed "decorative winding" as illustrated in FIGS. 1 and 2, has been employed for loading a magnetic tape.
In more detail, FIGS. 1 and 2 are schematic perspective views showing a tape winding body 2. In FIG. 1, a flexible endless belt 11 rotatably supported by rollers 12, 13 and 14 and formed of, for example, rubber, polyamide or the like, rotates together with a magnetic tape T so that the belt 11 elastically presses against the magnetic surface of the tape relatively strongly in the radial direction of the tape winding body 2 to thereby correct the winding appearance of the magnetic tape T. As shown in FIG. 2, a belt 15 formed of relatively soft unwoven fabric or the like is provided between a flange of a part of the tape winding body 2 and the edge of the magnetic tape T. While the belt 15, which is fed from a coiled belt supply roll 16, is wound through rollers 17 or the like onto a belt take-up roll 18 slowly at a constant speed, the belt 15 presses against one of the side edges of the tape relatively strongly to correct the winding appearance.
However, in either case, because the belt is in direct contact with the magnetic tape, dropout problems arise due to stripping of the magnetic layer caused by the unwoven fabric fiber or the like, deformation of the tape due to unsuitable pressure, and damage to the tape edges. Due to these problems, the original purpose of decorative winding often cannot be attained. Furthermore, the decorative winding mechanism has problems in regard to cost and maintenance.
Recently, a magnetic tape loading apparatus has been proposed, as shown in FIG. 3, in which the magnetic tape Tis wound onto a take-up reel 40 composed of a winding core 41 and a flange 42. At least one magnet 31 is disposed opposite to the site where the magnetic tape T is to be wound, arranged symmetrically with respect to the flange 42 and in the vicinity of winding driving shaft 30 detachably connected to the winding core 41. (See Japanese Laid-Open Patent Application No. 51642/1986.)
However, with the magnet 31 surrounding the shaft 30, the winding appearance in the inner portion of the tape near the winding core 41 is inferior to that in the outer portion of the tape. Moreover, the form of the magnet 31 is limited by the shaft 30. That is, the magnet 31 must be shaped like a doughnut. The direction of the magnetic force lines is thus not constant in the inner portion of the tape near the center of the reel 40, and the density of magnetic flux in that area becomes low. Accordingly, in the initial step of the winding process, the force attracting the magnetic tape T toward the flange 42 is unstable and weak. Particularly, the tape behavior at the beginning of the winding operation is very poor. In addition, in the case where the amount of friction between adjacent wound parts of the tape is large, a problem arises in that the effect of the magnet cannot be obtained if the magnetic force acting on the magnetic tape is not large. Accordingly, to correct for this problem, the size of the magnet must be large or, in the case of an electromagnet, the drive current applied to the magnet must be increased. Further, the tape winding speed range over which a good winding appearance can be obtained is limited.
Still further, a so-called "decompression winding method" has been proposed in which the loading apparatus is surrounded by a decompression chamber to reduce the ambient pressure below atmospheric pressure during tape winding. This method recognizes the fact that, when the magnetic tape is wound on the tape winding body, accompanying air is rolled up together with the tape, and the action of the air interposed between the winding layers causes the tape to slide in the direction of the tape width. Generally, the adverse influence of the air on the winding appearance becomes more remarkable as the tape winding speed is increased. Accordingly, the tape winding speed can be increased using the decompression method.
According to the aforementioned decompression winding method, as clearly shown by the tape speed curve and the decompression level curve in the graph of FIG. 4, winding of the tape is carried out between t.sub.1 and t.sub.2 (main decompression area) where the pressure level of the decompression chamber must be maintained at less than a predetermined value. In other words, the winding of the tape cannot be carried out in the time period between t.sub.0 and t.sub.1 where the decompression level is not sufficient, and similarly in the interval between t.sub.2 and t.sub.3 where the decompression level is reduced, because the amount of decompression in those periods is too small to obtain a good winding appearance. Accordingly, the total time required for winding the tape is increased by the sum of the time between t.sub.0 and t.sub.1 and the time between t.sub.2 and t.sub.3. This causes a problem in manufactirng efficiency.